


Monster

by Kallistni



Series: Good Kitty [1]
Category: One Piece
Genre: Anal Sex, Big Cock, Catboy Luffy, Crazy As Balls Trafalgar Law, Cum Inflation, Hurt No Comfort, I Wrote This Instead of Sleeping, I'm Going to Hell, I'm Sorry Luffy, M/M, No Lube, Non-Consensual, Not Canon Compliant, OOC, Possessive Behavior, Possessive Trafalgar Law, Psychopath Trafalgar Law, Rape, Sadistic Trafalgar Law, Stomach Bulge, The Author Regrets Everything, The Author Regrets Nothing, monster cock, no nothing, no prep
Language: English
Status: Completed
Published: 2017-09-03
Updated: 2017-09-03
Packaged: 2018-12-23 06:54:07
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 1
Words: 3,293
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11984505
Author URL: https://archiveofourown.org/users/Kallistni/pseuds/Kallistni
Summary: Mad scientist!Law has a surprise for his captive, Luffy.





	Monster

**Author's Note:**

> This fic was inspired by a story I read on ff.net in which Trafalgar Law kidnapped Luffy in order to perform experiments on him and ended up sexually assaulting him. If you've read that story then you will notice that I borrowed (stole?) a few key plot elements from it, but all you really need to know is:
> 
> -Law is fucking insane  
> -he kidnapped Luffy in order to perform experiments on him, most of which amount to force-feeding Luffy devil fruit and seeing if he survives  
> -the first of these experiments resulted in Luffy becoming a catboy
> 
> Note that this story should not be considered a continuation of that one in any way and that there are some important differences in the premise that will become apparent later in the series. I'm not playing in that author's sandbox; I just borrowed some sand.
> 
> This fic was originally much longer, but I ended up cutting the first two thirds because it was unsatisfactory and just not very interesting; for that reason, there are a few references left over to stuff that happened in the parts that were scrapped. I did my best to explain or remove them all, but if you catch any, that's why.
> 
> Trafalgar Law will be consistently referred to as Torao in scenes that are written from Luffy's POV. This is deliberate and not a mistake.
> 
> Trafalgar Law will not be using his devil fruit powers in this story because they are way OP and would have taken too much effort to work with given that I'm only writing this for fun. Just try to imagine that he could use them but inexplicably chooses not to, or maybe they're different and only useful in a medical context. idfk
> 
> If you're still with me after all that, kudos to you! I hope you enjoy the story.

Luffy tensed when the door to his cell jerked open, blinking repeatedly against the bright light flooding in from the hall. Torao tossed a hunk of meat onto the floor and Luffy scrambled forward to snatch it without a second thought. He retreated back into the corner and consumed it in two bites, wondering anxiously why his captor was being merciful today. 

He glanced up furtively, trying to gauge the other pirate's mood from his expression. Torao's mouth was drawn into a hard line, but underneath his indifferent exterior Luffy could sense the bottomless well of fury that had been mounting ever since Luffy had briefly gotten the upper hand several days earlier. So far Torao had been keeping it tightly contained, but Luffy was afraid of what was going to happen when all that rage finally boiled over. 

Luffy hadn't been surprised when Torao's most recent experiment had finally killed him, but waking up to discover that he was not only alive but had gained the ability to recover even from near-fatal injuries had been quite unexpected - Torao's experiments almost never worked, after all. 

He didn't regret what he'd done upon awakening to find that Torao had removed the seastone armband that kept his powers sealed. Punching his captor in the face over and over again had been immensely satisfying, and there was honestly no one who deserved it more. He did mourn the lost opportunity, though, very much so. He'd been so focussed on the fight that he hadn't noticed the older man picking up the tranquilizer gun until it was too late. Maybe if he'd tried to escape right away instead of beating Torao up he'd be free by now, and all this would just be a nightmare he'd try to forget come morning. 

How long had it been since he'd last seen the sun...? 

He didn't notice that Torao was holding something else until the man crouched down and placed it before him: it was a large glass of water, so cold that beads of condensation were rolling down its sides. Luffy glanced up at Torao suspiciously - fresh water had become a rarity as of late - but accepted it all the same, gulping it down and welcoming the relief it brought to his cracked lips and parched throat. 

When he put down the glass he found that Torao was sitting back on his heels and staring down at him in that eerily intense way he had that always made Luffy feel like ice cubes were sliding down his spine. "What do you want?" he asked warily, his voice cracking from disuse. Torao's small acts of kindness always came with a price. 

To his surprise, the older pirate suddenly smiled and said, "I've been feeling bad for leaving you here all alone for the past few days with nothing to do. So today we're gonna do an experiment, and then afterward I've got a surprise for you." 

Luffy's eyes narrowed suspiciously. "I don't want it." 

Smile smile. "Well, you're getting one." 

"What is it this time?" Luffy asked tiredly. "Another devil fruit?" 

Torao hesitated, glancing to the side a little as he replied, "No ... I decided that I'm finished with that series of experiments. I still can't figure out why none of the other test subjects are surviving the procedure, and after the first few you ate I stopped learning anything new. Besides..." The smile slipped off his face, and he shot Luffy a dirty look as he said, "I don't think you need any more powers. You're strong enough already." 

Luffy tried to jerk away when Torao reached for his arm, but he was backed into a corner and there was nowhere to go. Torao brought Luffy up with him as he stood and then grabbed him around the middle to throw him over his shoulder. Weakened by seastone and long days of hunger and dehydration, Luffy could only hang limply in Torao's hold. 

Once they got to the lab, Torao set Luffy down on the metal table in the center of the room before walking off and busying himself with something at the workstation set against the far wall. Luffy scooted forward so his legs dangled over the edge of the table, then forced himself to be still as he nervously waited for Torao to start whatever new torture he'd come up with. The older man worked for several minutes, whistling an annoyingly cheerful tune all the while. Luffy tensed when he came back holding a syringe, then became very confused when Torao winked at him before bringing the needle up to his neck and injecting _himself_. 

"What the hell was that?" Luffy asked nervously. 

"That was the experiment," Torao answered - or rather, didn't. "It's also part of your surprise." 

Luffy shifted uneasily. "What's the surprise?" 

Torao smirked. "You'll see." 

He reached into his pocket and pulled out a pair of matching bracelets made from what appeared to be polished steel. "This is the other part of your surprise," he said. He held one of the bracelets up for Luffy to inspect. "The outside is titanium, but the inside is treated seastone. It will still sap your strength and prevent you from using your powers at will, but the effects won't be quite as extreme as they were with the armband. See this?" 

He pointed at a thin line of silver that ran through the center of the bracelet's dark inner surface. "This is a wire that connects to a miniaturized power source on the inside of each bracelet. The circuits in there respond to voice commands - only mine, of course - and together they're capable of delivering a shock-like sensation so powerful that it'll even work on _you_. With your Gomu Gomu I suppose you've never had the privilige of experiencing electrocution before, have you, Luffy?" 

Luffy didn't bother dignifying that with a response. He glared at Torao, trembling slightly with a mixture of fear and disgust. "If your experiments with the devil fruit are over," he said quietly, "why can't you just let me go? Haven't you done enough to me already?" 

Torao chucked as if he'd just said something quite amusing. "Oh, Luffy," he said almost fondly, " _I'm just getting started_." 

*** 

The smaller man tried to resist, but Law easily overpowered him and pinned him against the table while he locked the new bracelets around Luffy's wrists. He checked to make sure they were secure, then removed the older armband and tossed it onto his desk. He wouldn't be needing it anymore, but it might come in handy if he needed to subdue another devil fruit user. 

Luffy became very tense when Law forced him to remove his clothes, but rather than following his usual routine he left Luffy on the table and went back to the other side of the room. He busied himself with some work while he waited for the serum to kick in, odds and ends that needed to be taken care of before he shut down the lab and headed back to his ship in a few days. Luffy was trying to pretend like he didn't care what Law was doing, but he was clearly on edge and his anxiety was almost palpable. No doubt he was going just about crazy trying to figure out what was going to happen next. Those cute little ears were flicked almost all the way back, and his tail kept twitching erratically. He looked so adorable that Law wanted to throw him to the floor right then and fuck him until he broke, but he forcibly restrained himself using a level of self control that he hadn't even been sure he had. 

He could wait. It wouldn't be long now. 

He managed to get quite a bit of work done before he started feeling the first hint of numbness in his extremities. Luffy, bless his heart, hadn't moved an inch; maybe he was finally accepting the realities of his situation. He may not like what Law would do with him at times, but things could always be a lot worse. Luffy seemed like he was starting to get that, but Law wanted to make sure that the lesson really stuck. 

He wasn't expecting any pain, but a mild burning sensation had been reported by about two thirds of the people he'd tested this formula on. So he wasn't surprised when his skin started to tingle and heat spread outward from his groin. It was an odd sensation, but not entirely unpleasant. He'd been hard basically since he'd dragged Luffy from his cell, but now his cock was really starting to throb, the skin beginning to feel like it was stretched just a bit too tight. He placed his hands flat against his desk and leaned against it, unable to stifle a gasp as the serum really started to take effect. 

"T-Torao?" he heard Luffy call nervously. His cock gave another twitch and it suddenly occurred to him that he'd better undo his pants, because they were starting to get a whole lot tighter. He fumbled to undo the buttons with one hand, needing the other to support his weight as his knees threatened to buckle under the onslaught of strange sensations. His cock felt alien in his hand as he pulled it out; it was shifting unnaturally and had already grown large enough to feel noticeably heavy. 

"Torao?" Luffy called again, sounding a little closer this time. 

"Stay on the table, Luffy," he ordered through gritted teeth. A glob of fluid dripped from the head of his cock and splattered against the floor, much too thick to be normal precum or even semen. 

"What's going on? What's happening to you?" his captive demanded, obviously distressed. 

"It's almost finished," Law growled back. "Be a good kitty and wait for your surprise." 

His breath was coming in pants now and his blood was pounding in his ears, but he still managed to pick up the sound of Luffy's breath hitching in time to whirl around and catch him the second he tried to bolt. He shoved Luffy to the floor and all but collapsed onto him, unable to suppress a groan of arousal when his erection slapped down against the younger man's flat little stomach. 

The horror he saw in Luffy's eyes when he caught a glimpse of Law's expanding cock was almost too much. Bracing himself against the floor with one arm, he buried his fingers in Luffy's hair and violently pressed their mouths together. 

Luffy moaned in protest as Law forced his tongue into his mouth. The younger man tasted as sweet as Law had always dreamed he would, but his ecstasy was cut short when Luffy bit down with razor-sharp teeth. Oh yeah, he remembered belatedly, _that_ was why he'd been holding off on his desire to give Luffy his first kiss. 

"Fuck!" Law yelped, grabbing Luffy's throat and pressing into the hinge of his jaw before the smaller man could bite too deep. He forced the brat's mouth open and drew back, turning his face slightly to the side so he could spit blood onto the floor. "You shouldn't have done that," he growled. "All of this could have been avoided if you'd only _been good_." 

"What the hell is that supposed to mean?" Luffy choked out. 

"You know that it's futile, but you keep trying to fight me," Law said irritably. "I saved your fucking life the other day, and you repaid me by beating me half to death. You think that I've been unfair to you? I have been fucking generous allowing you to draw breath after the shit you've put me through! So now you're gonna find out what happens when you're a bad kitty, and hopefully this time you'll get it through your thick skull that I'm not fucking around!" 

"What do you want from me?" Luffy protested, looking almost taken aback. "How the hell can you expect me to-" 

" _I expect you to do what I say,_ " Law said dangerously, "and to trust me when I tell you that things are only gonna get worse for you if you continue to piss me off." 

The tingling sensation was fading, and it felt like his cock wasn't growing anymore. 

Time to show Luffy exactly how serious he was. 

He released Luffy's throat and sat back on his heels, grabbing the boy's legs and spreading them around his hips before he could scramble away. Luffy froze when his gaze fell on the cock that was pressing into him from the crack of his ass to several inches above his belly button. 

Even Law, who had engineered the change and was familiar with its functions and intended usage, had to admit that it wasn't pretty; to Luffy, it probably looked monstrous. Thicker than a bottle of rum with a bulbous head that leaked thick globs of precum, it was covered in irregular lumps and protrusions that would scrape against Luffy's inner walls once he got inside. It was also much more sensitive than an ordinary cock and would have a much shorter recovery rate, but that was just for Law. The enhanced semen production, on the other hand, would no doubt prove interesting for the both of them. 

"No, no, no, no, Torao, please, no, you can't," Luffy babbled, slitted pupils shrinking to pinpricks with the force of his terror. The bumps on Law's new cock felt amazing rubbing against the soft skin on Luffy's stomach as he pulled back, back, back to press its large, blunt head against Luffy's tiny hole. 

He could honestly say that he'd never been more aroused. 

He only got half the head in on his first thrust, but Luffy screamed like he was dying. Law had to keep a tight grip on the younger man's hips to prevent him from scrambling away. The seastone he'd used was weak enough that it was allowing Luffy to stretch beyond what would be possible for a normal human, but it was still a damn tight fit. It took three more thrusts before the head slid in with an audible pop, and by then Luffy was trembling so hard that it almost felt like he was vibrating. Luffy's inner muscles continuously spasmed around him trying to push him out, but only succeeded in giving him a pleasurable massage that spurred him into thrusting harder. 

Had Luffy always been this hot inside, this soft? Law had been addicted from the moment he'd first tasted Luffy's charms weeks before, but this was on a whole new level. This was like storming the gates of heaven, punching God in the face, and getting his cock sucked by a million angels. This ... this was _perfection_. 

Right then, he vowed to himself that he was never going to let Luffy go. No one, not the marines nor Luffy's crew nor even death itself, would be permitted to take Luffy away from him. Luffy was going to be with him until the day Law died. 

"Good kitty," he panted, forcing in another half an inch. Luffy was sobbing desperately, tears running down his cheeks in a steady stream. Law bent down and ran his tongue over one reddened cheek, savoring the delicate taste of salt. 

Blood splattered down the backs of Luffy's thighs on his first withdrawal, but he wasn't too concerned; he was pretty sure that the younger man would heal quickly enough that it wouldn't become a problem. He had much more important things to focus on, in any case, like burying himself as deeply as possible and nailing the pretty little cat into the floor. 

Despite Law's enthusiasm, it must have taken more than twenty minutes for him to force his entire cock into Luffy's ass. Once he'd finally succeeded, he had to stop for a few seconds to regain his breath and just savor the sensation of blood-slicked heat gripping him like a vice. He looked down and his cock jerked when he saw that there was a very noticeable lump bulging out of Luffy's stomach in exactly the shape of his erection. He inhaled shakily and traced it with one hand, feeling a little awed. When he pressed down on it Luffy screamed, though it came out more as a squeak since his voice had long since given out. 

It was difficult to get into a rhythm with Luffy's hole squeezing him so tightly, but eventually he got the hang of it and was able to increase his speed. The thickness of his precum helped to smooth the way, though nothing could prevent Luffy's insides from clinging to the protrusions on his cock every time he moved. 

He didn't last nearly as long as he wanted to, but it was long enough that Luffy was a shivering wreck by the time he finally pushed in as deep as he could go and felt release come crashing through him like a tidal wave. Paste-like semen flooded into Luffy's ass in audible spurts, pouring out by what felt like the cupful. His orgasm lasted for nearly an entire minute, and by the end of it Luffy was moaning in pain and his stomach was bulged out like he was four months pregnant. Even as his cock started to deflate, Luffy's hole clung to it so tightly that nothing could escape. Law was a little bit fascinated, but felt too exhausted at the moment to investigate the phenomenon. 

He didn't bother pulling out of Luffy's ass as his orgasm died down. If the serum had worked as it should, it would only be a few minutes until he was up for round two. 

*** 

Law's lab looked different with all the equipment shut down, he thought. It seemed emptier somehow, completely devoid of life. Or maybe he was only feeling that way because he'd just returned from culling the last of the test subjects that had been left over from the series of experiments he'd just concluded. 

Either way, he thought that he was actually going to miss this place. He'd only been staying there for a couple months, but he'd made a lot of good memories in that time. 

Good thing he was taking the best part with him. 

Luffy accepted the raincoat sullenly, slipping it on without protest. It was black and much too large on him - perfect for hiding his ears, face, and tail. Law had been tempted to give Luffy a sedative for the trip, but carrying an unconscious person through town would draw too much suspicion. At least this way, if anyone questioned him he could just say his friend hurt his ankle. 

"Now, before we go, remind me: what will happen if you struggle, protest, ask for help, or try to get away from me in any form?" 

"You'll choke me out, kill everyone who saw, and rape me for six hours as soon as we get back to your ship," Luffy muttered reluctantly, glaring down at the floor like he wished it would swallow him up. 

"Very good," Law praised him, threading his fingers through Luffy's hair and scratching him behind the ears. Luffy's tail twitched and he flushed ever so slightly like he couldn't decide whether it felt good or not. 

Well, they'd get there. 

Law pulled up Luffy's hood and checked him over a couple times to make sure he was sufficiently covered. Then he picked Luffy up and headed toward the exit, turning the lights off as he went. 

"Hey, Torao," Luffy murmured, glancing up at him from under the edge of his hood. 

"Yeah?" Law said curiously. 

"When is ... I mean, how long ... when is _it_ gonna go back to normal?" 

Law paused, then looked down at Luffy with a smirk. 

"It doesn't." 


End file.
